Electrical storage system

ABSTRACT

Charging of an electrical storage device is completed by operation-starting time while increasing a percentage of a charging time of the electrical storage device in a first time period as compared to a percentage of the charging time in a second time period when the first time period and the second time period are included within a period from when a user sets the operation-starting time to the operation-starting time. A temperature adjustment device is operated such that a temperature of the electrical storage device at the operation-starting time falls within a target temperature range while increasing a percentage of an operating time of the temperature adjustment device in the first time period as compared to a percentage of the operating time in the second time period when the first time period and the second time period are included within the period from when the user sets the operation-starting time to the operation-starting time. The operation-starting time is scheduled time at which a start-up of a vehicle is initiated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an electrical storage system that charges anelectrical storage device with electric power from a commercial powersupply and that adjusts the temperature of the electrical storagedevice.

2. Description of Related Art

In Japanese Patent Application Publication No. 2011-259672 (JP2011-259672 A), an electrical storage device is charged from an externalpower supply, a user is allowed to set time at which the charging iscompleted (referred to as charging completion time). When the chargingcompletion time is set, the electrical storage device is charged suchthat charging of the electrical storage device completes at the chargingcompletion time. In JP 2011-259672 A, in order to bring the temperatureof the electrical storage device at the charging completion time into apredetermined temperature range, a fan for cooling the electricalstorage device is operated until the charging completion time when thetemperature of the electrical storage device is high.

In a vehicle on which the electrical storage device is mounted, a useris allowed to set time at which a start-up of the vehicle is initiated(referred to as operation-starting time). In JP 2011-259672 A, when theoperation-starting time is set, the charging completion time is set forthe operation-starting time. In order to bring the temperature of theelectrical storage device at the operation-starting time into thepredetermined temperature range, when the temperature of the electricalstorage device is high, the fan for cooling the electrical storagedevice is operated until the operation-starting time.

Usually, a commercial power supply is used as an external power supply,the cost of electricity of the commercial power supply can depend on atime period of a day. The charging completion time (or theoperation-starting time) is arbitrarily set by a user, so there may betime periods of different costs of electricity within a period from thetime at which charging is initiated to the charging completion time (orthe operation-starting time). In such a case, as described in JP2011-259672 A, if the electrical storage device is charged such that thecharging of the electrical storage device completes at the chargingcompletion time (or the operation-starting time), the electrical storagedevice can be charged more intensively in a time period during which thecost of electricity is high than in a time period during which the costof electricity is low. Such charging of the electrical storage deviceburdens the user with an excessive cost of electricity.

On the other hand, when the fan is operated as in the case of JP2011-259672 A, electric power from the external power supply (commercialpower supply) is allowed to be used. As described in JP 2011-259672 A,in the case where the fan is operated such that the temperature of theelectrical storage device falls within the predetermined temperaturerange at the charging completion time (or the operation-starting time),if there are time periods of different costs of electricity within aperiod up to the charging completion time (or the operation-startingtime), the fan can be operated intensively in a time period during whichthe cost of electricity is high. Such operation of the fan results inburdening the user with an excessive cost of electricity.

SUMMARY OF THE INVENTION

An aspect of the invention provides an electrical storage system. Theelectrical storage system includes: an electrical storage device mountedon a vehicle and configured to be charged with electric power suppliedfrom a commercial power supply; a temperature adjustment deviceconfigured to adjust a temperature of the electrical storage device uponreception of electric power supplied from the commercial power supply;and a controller configured to control charging of the electricalstorage device and operation of the temperature adjustment device. Thecommercial power supply is set such that a cost of electricity of afirst time period is lower than a cost of electricity of a second timeperiod.

The controller is configured to complete charging of the electricalstorage device by operation-starting time while increasing a percentageof a charging time of the electrical storage device in the first timeperiod as compared to a percentage of the charging time in the secondtime period when the first time period and the second time period areincluded within a period from when a user sets the operation-startingtime to the operation-starting time. The operation-starting time isscheduled time at which a start-up of the vehicle is initiated. Byincreasing the percentage of the charging time of the electrical storagedevice in the first time period as compared to the percentage of thecharging time in the second time period, it is possible to charge theelectrical storage device by actively utilizing the first time period ofwhich the cost of electricity is low. Thus, even when the userarbitrarily sets the operation-starting time, it is possible to reduce acost of electricity required to charge the electrical storage device.

The controller is configured to operate the temperature adjustmentdevice such that a temperature of the electrical storage device at theoperation-starting time falls within a target temperature range whileincreasing a percentage of an operating time of the temperatureadjustment device in the first time period as compared to a percentageof the operating time in the second time period when the first timeperiod and the second time period are included within the period fromwhen the user sets the operation-starting time to the operation-startingtime.

By increasing the percentage of the operating time of the temperatureadjustment device in the first time period as compared to the percentageof the operating time in the second time period, it is possible tooperate the temperature adjustment device by actively utilizing thefirst time period of which the cost of electricity is low. Thus, evenwhen the user arbitrarily sets the operation-starting time, it ispossible to reduce a cost of electricity required to operate thetemperature adjustment device.

By bringing the temperature of the electrical storage device at theoperation-starting time into the target temperature range through theoperation of the temperature adjustment device, it becomes easy toensure the input/output performance of the electrical storage device atthe operation-starting time. Because the input/output performance of theelectrical storage device depends on the temperature of the electricalstorage device, it is possible to initiate a start-up of the vehicle ina state where the input/output performance of the electrical storagedevice is ensured by bringing the temperature of the electrical storagedevice into the target temperature range.

When the operation of the temperature adjustment device is completedearlier than the operation-starting time, a temperature variation in theelectrical storage device within the period from when the operation ofthe temperature adjustment device is completed to the operation-startingtime may be estimated from a temperature of a surrounding environment ofthe electrical storage device. When the operation of the temperatureadjustment device is completed, the temperature of the electricalstorage device is influenced by the temperature of the surroundingenvironment of the electrical storage device. Therefore, it is possibleto acquire the temperature variation in the electrical storage device onthe basis of the temperature of the surrounding environment.

The temperature variation in the electrical storage device indicates avalue obtained by subtracting the temperature of the electrical storagedevice at the time when the operation of the temperature adjustmentdevice is completed from the temperature of the electrical storagedevice at the operation-starting time. When the estimated temperaturevariation is a negative value, it appears that the temperature of theelectrical storage device decreases after the operation of thetemperature adjustment device is completed. Therefore, the temperatureof the electrical storage device may be increased in advance inconsideration of the temperature variation (the amount of decrease intemperature) by the time when the operation of the temperatureadjustment device is completed, and it is possible to bring thetemperature of the electrical storage device at the operation-startingtime into the target temperature range. Specifically, the temperature ofthe electrical storage device at the time when the operation of thetemperature adjustment device is completed may be increased as comparedto an upper limit value of the target temperature range by thetemperature variation.

When the temperature of the electrical storage device at the time whenthe temperature of the electrical storage device has been increased bythe temperature variation becomes higher than an upper limit temperaturethat is allowed by the electrical storage device (allowable upper limittemperature), the temperature of the electrical storage device may beincreased to the allowable upper limit temperature. In other words, thetemperature of the electrical storage device may not be increased to atemperature higher than the allowable upper limit temperature. Thus, itis possible to suppress generation of abnormal heat in the electricalstorage device by suppressing an increase in the temperature of theelectrical storage device above the allowable upper limit temperaturewhen the temperature adjustment device is being operated.

When the estimated temperature variation is a positive value, it appearsthat the temperature of the electrical storage device increases afterthe operation of the temperature adjustment device is completed.Therefore, the temperature of the electrical storage device may bereduced in advance in consideration of the temperature variation (theamount of increase in temperature) by the time when the operation of thetemperature adjustment device is completed, and it is possible to bringthe temperature of the electrical storage device at theoperation-starting time into the target temperature range. Specifically,the temperature of the electrical storage device at the time when theoperation of the temperature adjustment device is completed may bereduced as compared to a lower limit value of the target temperaturerange by the temperature variation.

When the operation-starting time is later than the termination time ofthe first time period, it becomes easy to reduce a cost of electricityrequired to operate the temperature adjustment device by sufficientlyutilizing the first time period as a time during which the temperatureadjustment device is operated. For example, it is possible to operatethe temperature adjustment device until the termination time of thefirst time period. When the operation of the temperature adjustmentdevice is completed by the termination time of the first time period,the temperature variation in the electrical storage device within theperiod from when the operation of the temperature adjustment device iscompleted to the operation-starting time may be estimated, and then thetemperature adjustment device may be operated such that the temperatureof the electrical storage device at the operation-starting time fallswithin the target temperature range, as described above.

Electric power from the commercial power supply is used when theelectrical storage device is charged or when the temperature adjustmentdevice is operated. Therefore, the temperature adjustment device may beoperated while the electrical storage device is charged. By operatingthe temperature adjustment device while charging the electrical storagedevice, it becomes easy to bring the temperature of the electricalstorage device at the operation-starting time into the targettemperature range. Particularly, when charging of the electrical storagedevice completes before the operation-starting time, it is possible tobring the temperature of the electrical storage device close to thetarget temperature range by the time when the charging of the electricalstorage device completes by operating the temperature adjustment devicewhile charging the electrical storage device.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a view that shows the configuration of a battery system;

FIG. 2 is a view that shows the configuration of a circuit for operatinga temperature adjustment device;

FIG. 3 is a flowchart that shows the process of carrying out externalcharging;

FIG. 4 is a flowchart that shows the process of carrying out externalcharging while adjusting the temperature of a battery pack;

FIG. 5 is a graph that shows the correlation between input and outputupper limit values and the temperature of the battery pack;

FIG. 6 is a flowchart that shows the process of adjusting thetemperature of the battery pack after external charging;

FIG. 7 is a flowchart that shows a heating process after externalcharging;

FIG. 8 is a flowchart that shows a cooling process after externalcharging;

FIG. 9 is a time chart that shows a change in battery temperature at thetime when the heating process is executed;

FIG. 10 is a time chart that shows a change in battery temperature atthe time when the cooling process is executed;

FIG. 11 is a flowchart that illustrates a time during which externalcharging is carried out;

FIG. 12A to FIG. 12D are time charts each showing the correlation amonga midnight time period, current time and charging completion time;

FIG. 13 is a flowchart that illustrates a time during which thetemperature adjustment process is executed; and

FIG. 14A and FIG. 14B are graphs each showing a time period during whichexternal charging is carried out and the cooling process is executed,and a change in battery temperature.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the invention will be described.

FIG. 1 is a view that shows the configuration of a battery system (whichcorresponds to the electrical storage system according to the invention)according to the present embodiment. The battery system shown in FIG. 1is mounted on a vehicle. The vehicle is, for example, a plug-in hybridvehicle (PHV) or an electric vehicle (EV).

The PHV includes not only a battery pack (described later) as a powersource for propelling the vehicle but also another power source, such asan engine and a fuel cell. The EV includes only the battery pack(described later) as a power source for propelling the vehicle. In thePHV and the EV, as will be described later, the battery pack is allowedto be charged with electric power from a commercial power supply.

The battery pack 10 includes a plurality of serially connected singlecells 11. An alkaline secondary battery, such as a nickel-metal hydridebattery and a nickel-cadmium battery, may be used as each single cell11. The battery pack 10 functions as an electrical storage device.Instead of the secondary battery, an electric double layer capacitor maybe used. The number of the single cells 11 may be set as needed on thebasis of a required output, or the like, of the battery pack 10. In thebattery pack 10 according to the present embodiment, all the singlecells 11 are electrically connected in series with each other; instead,the battery pack 10 may include a plurality of the single cells 11 thatare electrically connected in parallel with each other.

A monitoring unit 20 detects the voltage value Vb of the battery pack 10or detects the voltage value Vb of each single cell 11, and outputs thedetected result to a controller 30. A temperature sensor 21 detects thetemperature Kb of the battery pack 10 (single cells 11), and outputs thedetected result to the controller 30. One or a plurality of thetemperature sensors 21 may be arranged for the battery pack 10. Whenthere are variations in temperature among the plurality of single cells11 depending on the locations at which the single cells 11 are arranged,it is possible to acquire variations in temperature by using theplurality of temperature sensors 21.

A current sensor 22 detects the current value Ib of the battery pack 10,and outputs the detected result to the controller 30. In the presentembodiment, the current sensor 22 is provided in a positive electrodeline PL connected to the positive electrode terminal of the battery pack10. The current sensor 22 just needs to be able to detect the currentvalue Ib of the battery pack 10. The location at which the currentsensor 22 is provided may be set as needed. For example, the currentsensor 22 may be provided in a negative electrode line NL connected tothe negative electrode terminal of the battery pack 10. A plurality ofthe current sensors 22 may be used.

The controller 30 includes a memory 31. The memory 31 stores variouspieces of information, which are used by the controller 30 to execute apredetermined process (particularly, a process described in the presentembodiment). In the present embodiment, the memory 31 is incorporated inthe controller 30; instead, the memory 31 may be provided outside thecontroller 30. A clock 32 outputs information about current time Tc tothe controller 30. The clock 32 may be, for example, an atomic clock.The atomic clock has the function of automatically correcting an errorof time by receiving a standard wave.

An outside air temperature sensor 33 detects the temperature (referredto as outside air temperature) Ke of a surrounding environment of thebattery pack 10, and outputs the detected result to the controller 30.The outside air temperature Ke is not the temperature Kb of the batterypack 10 but the temperature of a surrounding environment that thermallyinfluences the battery pack 10. For example, the outside air temperatureKe may be the temperature of a space (surrounding environment) in whichthe battery pack 10 is mounted or may be a temperature in the outside(surrounding environment) of the vehicle.

An input unit 34 is used by a user to input specific information.Information input from the input unit 34 is output to the controller 30.Information input from the input unit 34 may be stored in the memory 31.The input information may be, for example, time Te at which externalcharging is completed (referred to as charging completion time), time TUat which a start-up of the vehicle is initiated (referred to asoperation-starting time), initial time. TMs from which a midnight costof electricity (described later) is applied (referred to as midnightrate initial time) or termination time TMe until which the midnight costof electricity is applied (referred to as midnight rate terminationtime) TMe. As will be described later, external charging is to chargethe battery pack 10 with electric power from the commercial powersupply. The user is allowed to set the charging completion time Te byoperating the input unit 34. When the charging completion time Te isset, the battery system shown in FIG. 1 is able to complete externalcharging by the charging completion time Te.

The operation-starting time TU is time at which the user will initiate astart-up of the vehicle in the future. The operation-starting time TU isallowed to be set by user's operation of the input unit 34. Theoperation-starting time TU is time at or after the charging completiontime Te. In the present embodiment, the input unit 34 is mounted on thevehicle; however, the input unit 34 is not limited to this arrangement.For example, the charging completion time Te and/or theoperation-starting time TU may be set by user's operation of a mobileterminal via wireless communication. In this case, the vehicle justneeds to include a receiving unit that receives transmission information(information for setting the charging completion time Te and/or theoperation-starting time TU) from the mobile terminal. Specifically,instead of the input unit 34 or in addition to the input unit 34, thereceiving unit may be provided.

The cost of electricity of the commercial power supply depends on a timeperiod of a day. In the present embodiment, the cost of electricity of amidnight time period (midnight cost of electricity) is lower than thecost of electricity of a time period other than the midnight timeperiod. The midnight time period is regarded as a first time period. Thetime period other than the midnight time period is regarded as a secondtime period. The midnight time period is usually set by the businessoperator of the commercial power supply. The user is allowed to set themidnight rate initial time TMs and/or the midnight rate termination timeTMe by operating the input unit 34.

In the present embodiment, in prospect of a situation that the midnightrate initial time TMs and/or the midnight rate termination time TMe arechanged, the midnight rate initial time TMs and/or the midnight ratetermination time TMe are configured to be input through the input unit34. When the midnight rate initial time TMs and/or the midnight ratetermination time TMe are not changed, information about the midnightrate initial time TMs and/or the midnight rate termination time TMe maybe stored in the memory 31 in advance. On the other hand, it is possibleto set the midnight rate initial time TMs and/or the midnight ratetermination time TMe by operating a mobile terminal without using theinput unit 34. In this case, a receiving unit that receives transmissioninformation (information for setting the midnight rate initial time TMsand/or the midnight rate termination time TMe) from the mobile terminaljust needs to be provided in the vehicle. The receiving unit may beprovided in the vehicle in addition to the input unit 34 or instead ofthe input unit 34.

A system main relay SMR-B is provided in the positive electrode line PL.The system main relay SMR-B switches between an on state and an offstate upon reception of a control signal from the controller 30. Asystem main relay SMR-G is provided in the negative electrode line NL.The system main relay SMR-G switches between an on state and an offstate upon reception of a control signal from the controller 30.

When the battery pack 10 is connected to an inverter 24, the controller30 switches the system main relays SMR-B, SMR-G from the off state tothe on state. Thus, the battery system shown in FIG. 1 enters anactivated state (ready-on state). Information about the on/off state ofan ignition switch of the vehicle is input to the controller 30. Thecontroller 30 starts up the battery system shown in FIG. 1 in responseto the switching of the ignition switch from the off state to the onstate.

On the other hand, when connection of the battery pack 10 with theinverter 24 is interrupted, the controller 30 switches the system mainrelays SMR-B, SMR-G from the on state to the off state. Thus, thebattery system shown in FIG. 1 enters a stopped state (ready-off state).When the ignition switch is switched from the on state to the off state,the controller 30 causes the battery system to enter the stopped state.

The inverter 24 converts direct-current power, output from the batterypack 10, to alternating-current power, and outputs thealternating-current power to a motor generator (MG) 25. The motorgenerator 25 generates kinetic energy for propelling the vehicle uponreception of the alternating-current power output from the inverter 24.The kinetic energy generated by the motor generator 25 is transmitted towheels, thus causing the vehicle to travel.

When the vehicle is decelerated or the vehicle is stopped, the motorgenerator 25 converts kinetic energy, generated during braking of thevehicle, to electric energy (alternating-current power). The inverter 24converts alternating-current power, generated by the motor generator 25,to direct-current power, and outputs the direct-current power to thebattery pack 10. Thus, the battery pack 10 stores regenerative electricpower.

In the present embodiment, the battery pack 10 is connected to theinverter 24; however, the battery pack 10 is not limited to thisconfiguration. Specifically, a step-up circuit may be provided in acurrent path between the battery pack 10 and the inverter 24. Thestep-up circuit is able to step up the output voltage of the batterypack 10 and then to output the stepped-up electric power to the inverter24. The step-up circuit is able to step down the output voltage of theinverter 24 and then to output the stepped-down electric power to thebattery pack 10.

A charger 26 is connected to the positive electrode line PL and thenegative electrode line NL via charging lines PCL, NCL. Specifically,the charging line PCL is connected to the positive electrode line PLbetween the system main relay SMR-B and the inverter 24. The chargingline NCL is connected to the negative electrode line NL between thesystem main relay SMR-G and the inverter 24. The location at which thecharging line PCL is connected to the positive electrode line PL and/orthe location at which the charging line NCL is connected to the negativeelectrode line NL may be set as needed.

Charging relays Rch1, Rch2 are respectively provided in the charginglines PCL, NCL. The charging relays Rch1, Rch2 switch between an onstate and an off state upon reception of a control signal from thecontroller 30. An inlet (connector) 27 is connected to the charger 26.

A plug (so-called connector) 29 connected to the commercial power supply28 is connected to the inlet 27. By connecting the plug 29 to the inlet27, it is possible to supply electric power, supplied from thecommercial power supply 28, to the battery pack 10 via the charger 26.Thus, it is possible to charge (externally charge) the battery pack 10from the commercial power supply 28. The charger 26 convertsalternating-current power, supplied from the commercial power supply 28,to direct-current power, and outputs the direct-current power to thebattery pack 10. The controller 30 is able to control the operation ofthe charger 26.

The battery system according to the present embodiment is able to carryout external charging when the system main relays SMR-B, SMR-G are inthe on state and the charging relays Rch1, Rch2 are in the on state.When external charging is carried out, it is possible to supply aconstant current to the battery pack 10, and it is possible to chargethe battery pack 10 at a constant current.

A system of supplying electric power from the commercial power supply 28to the battery pack 10 is not limited to the configuration shown inFIG. 1. In the present embodiment, the charger 26 is mounted on thevehicle; instead, a charger (referred to as external charger) may beinstalled outside the vehicle. In this case, the charger 26 shown inFIG. 1 is omitted. By connecting the plug 29, connected to the externalcharger, to the inlet 27, it is possible to supply the battery pack 10with electric power from the commercial power supply 28.

In the present embodiment, external charging is carried out byconnecting the plug 29 to the inlet 27; however, external charging isnot limited to this configuration. Specifically, it is possible tosupply electric power from the commercial power supply 28 to the batterypack 10 by employing a so-called contactless charging system. In thecontactless charging system, it is possible to supply electric power byutilizing electromagnetic induction or a resonance phenomenon withoutany intervening cable. A known configuration may be employed as thecontactless charging system as needed.

A system that adjusts the temperature of the battery pack 10 will bedescribed with reference to FIG. 2.

A temperature adjustment device 41 is used to adjust the temperature ofthe battery pack 10. The temperature adjustment device 41 is connectedto a DC/DC converter 42 via a relay TDR. The DC/DC converter 42 isconnected to the commercial power supply 28. When the relay TDR is in anon state, the DC/DC converter 42 supplies the temperature adjustmentdevice 41 with electric power from the commercial power supply 28. Thus,it is possible to operate the temperature adjustment device 41. Therelay TDR switches between an on state and an off state upon receptionof a control signal from the controller 30.

When the DC/DC converter 42 is connected to the commercial power supply28, the charging lines PCL, NCL shown in FIG. 1 are allowed to be usedor the positive electrode line PL and the negative electrode line NL areallowed to be used. That is, the DC/DC converter 42 just needs to beconnected to a path through which electric power is supplied from thecommercial power supply 28 to the battery pack 10. Thus, it is possibleto supply electric power, supplied from the commercial power supply 28,to not only the battery pack 10 but also the temperature adjustmentdevice 41.

In order to adjust the temperature of the battery pack 10, the batterypack 10 just needs to be cooled or the battery pack 10 just needs to beheated. When the battery pack 10 is cooled, for example, a Peltierelement or a compressor heat pump may be used as the temperatureadjustment device 41. The Peltier element generates heat or absorbs heatin response to a direction of flow of current and a current value.

When the battery pack 10 is cooled by supplying the battery pack 10 witha cooling heat exchanging medium (air, liquid, or the like), it ispossible to cool the heat exchanging medium, which is supplied to thebattery pack 10, by absorbing heat with the use of the Peltier element.The compressor heat pump is able to cool a heat exchanging medium, whichis supplied to the battery pack 10, by drawing heat from the heatexchanging medium. The heat of the heat exchanging medium is drawn byreducing the temperature of a heat medium through decompression of theheat medium. When the cooled heat exchanging medium is supplied to thebattery pack 10, it is possible to reduce the temperature Kb of thebattery pack 10.

When the battery pack 10 is heated, for example, a heater, a Peltierelement or a compressor heat pump may be used as the temperatureadjustment device 41. When current is supplied to the heater, it ispossible to generate heat from the heater. It is possible to heat a heatexchanging medium (air, liquid, or the like), which is supplied to thebattery pack 10, with the heat generated from the heater. When currentin a predetermined direction is passed through the Peltier element, itis possible to generate heat from the Peltier element. It is possible toheat the heat exchanging medium, which is supplied to the battery pack10, with the heat generated from the Peltier element. The compressorheat pump is able to heat the heat exchanging medium, which is suppliedto the battery pack 10, by increasing the temperature of a heat mediumthrough compression of the heat medium. When the heated heat exchangingmedium is supplied to the battery pack 10, it is possible to increasethe temperature Kb of the battery pack 10.

In the above description, the heat exchanging medium that is supplied tothe battery pack 10 is cooled or heated by the temperature adjustmentdevice 41; however, the configuration of cooling or heating the batterypack 10 is not limited to this configuration. Specifically, the batterypack 10 may be cooled or heated by directly or indirectly bringing thetemperature adjustment device 41 into contact with the battery pack 10.

Next, the process of carrying out external charging and the process ofadjusting the temperature of the battery pack 10 will be described withreference to the flowchart shown in FIG. 3 and FIG. 4. The process shownin FIG. 3 and FIG. 4 is executed by the controller 30. When the processshown in FIG. 3 and FIG. 4 is initiated, the plug 29 has been connectedto the inlet 27. When the charging completion time Te and/or theoperation-starting time TU have been set, the process shown in FIG. 3and FIG. 4 is initiated.

In step S101, the controller 30 acquires current time Tc from the clock32. In step S102, the controller 30 acquires the charging completiontime Te on the basis of the input information from the input unit 34. Instep S103, the controller 30 calculates a current state of charge (SOC)of the battery pack 10. The SOC is the ratio of a current level ofcharge to a full charge capacity. A known method may be used as neededas a method of calculating the SOC. It is possible to calculate the SOCof the battery pack 10 by using the detected results of the monitoringunit 20 and current sensor 22.

In step S104, the controller 30 calculates a processing time ΔTp ofexternal charging. The processing time ΔTp is a time that is taken whenthe battery pack 10 is charged from the current SOC to an SOC at thetime of completion of external charging (referred to as target valueSOC_targ). A value calculated in the process of step S103 is used as thecurrent SOC. The target value SOC_targ is set in advance. The targetvalue SOC_targ may be stored in the memory 31 as a fixed value. Thetarget value SOC_targ may be set by operating the input unit 34.

Because external charging is carried out at a constant current, acurrent integrated value is allowed to be calculated by multiplying thecurrent value by a time (charging time), and a variation in SOC isallowed to be calculated from the current integrated value. The chargingtime during which a variation in SOC coincides with a differentialbetween the current SOC and the target value SOC_targ is the processingtime ΔTp. When the current value for carrying out external charging isset in advance, it is possible to calculate the processing time ΔTp withthe above-described method.

In step S105, the controller 30 determines whether a time between thecurrent time Tc and the charging completion time Te is longer than theprocessing time ΔTp. The current time Tc and the charging completiontime Te are respectively obtained in the processes of step S101 and stepS102. The processing time ΔTp is calculated in the process of step S104.When the time between the current time Tc and the charging completiontime Te is longer than the processing time ΔTp, the controller 30executes the process of step S110 shown in FIG. 4. On the other hand,when the time between the current time Tc and the charging completiontime Te is shorter than or equal to the processing time ΔTp, thecontroller 30 determines that it is required to initiate externalcharging, and executes the process of step S106.

In step S106, the controller 30 initiates external charging. Thus,electric power is supplied from the commercial power supply 28 to thebattery pack 10, and the SOC of the battery pack 10 increases. In stepS107, the controller 30 calculates the SOC of the battery pack 10 duringexternal charging. In step S108, the controller 30, determines whetherthe SOC calculated in the process of step S107 is higher than or equalto the target value SOC_targ.

When the SOC of the battery pack 10 is lower than the target valueSOC_targ, the controller 30 continues external charging, and returns tothe process of step S107. On the other hand, when the SOC of the batterypack 10 is higher than or equal to the target value SOC_targ, thecontroller 30 completes external charging by controlling the operationof the charger 26 in step S109.

When external charging is carried out through the processes of step S106to step S109, it is possible to adjust the temperature Kb of the batterypack 10. Even when the time between the current time Tc and the chargingcompletion time Te is shorter than or equal to the processing time ΔTp,part of electric power, which is supplied from the commercial powersupply 28 to the battery pack 10, is allowed to be supplied to thetemperature adjustment device 41 depending on, for example, the actualprogress of external charging. Thus, it is possible to adjust thetemperature Kb of the battery pack 10 by operating the temperatureadjustment device 41.

When the controller 30 proceeds from the process of step S105 in FIG. 3to the process of step S110 in FIG. 4, the controller 30 determines thatit is possible to adjust the temperature Kb of the battery pack 10 whilecarrying out external charging. When the time between the current timeTc and the charging completion time Te is longer than the processingtime ΔTp, it is possible to sufficiently ensure the time during whichthe temperature Kb of the battery pack 10 is adjusted.

Time at which the process from step S110 is initiated may be set asneeded. That is, external charging just needs to be completed by thecharging completion time Te. Specifically, it is possible to determinethe time, at which the process from step S110 is initiated, inconsideration of the processing time ΔTp and the charging completiontime Te.

In step S110, the controller 30 initiates external charging. In stepS111, the controller 30 detects the temperature (battery temperature) Kbof the battery pack 10 on the basis of the output of the temperaturesensor 21. In step S112, the controller 30 determines whether thebattery temperature Kb is lower than a target temperature Ktarg. Thevalue detected in the process of step S111 is used as the batterytemperature Kb.

The target temperature Ktarg is a temperature set in advance on thebasis of the viewpoint of ensuring the input/output performance(charge/discharge performance) of the battery pack 10. Because theinput/output performance of the battery pack 10 depends on thetemperature Kb of the battery pack 10, an appropriate temperature forensuring the input/output performance is allowed to be set as the targettemperature Ktarg. Information regarding the target temperature Ktarg(information that specifies the target temperature Ktarg) may be storedin the memory 31.

When the output of the battery pack 10 is controlled, an upper limitvalue Wout at or below which the output power of the battery pack 10 isallowed is set, and the output of the battery pack 10 is controlled suchthat the output power of the battery pack 10 does not exceed the upperlimit value Wout. When the input of the battery pack 10 is controlled,an upper limit value Win at or below which the input power of thebattery pack 10 is allowed is set, and the input of the battery pack 10is controlled such that the input power of the battery pack 10 does notexceed the upper limit value Win.

As shown in FIG. 5 (one example), the upper limit values Wout, Winchange in response to the battery temperature Kb. Specifically, when thebattery temperature Kb falls between temperatures Kb1, Kb2 (Kb1<Kb2),the upper limit values Wout, Win are respectively set to maximum valuesWout_max, Win_max. When the battery temperature Kb is lower than thetemperature Kb1, the upper limit values Wout, Win are respectivelyreduced from the maximum values Wout_max, Win_max. When the batterytemperature Kb is higher than the temperature Kb2, the upper limitvalues Wout, Win are respectively reduced from the maximum valuesWout_max, Win_max. A temperature at which the upper limit value Wout isreduced may be different from a temperature at which the upper limitvalue Win is reduced.

As is apparent from FIG. 5, when the battery temperature Kb fallsbetween the temperatures Kb1, Kb2, the upper limit values Wout, Win arerespectively set to the maximum values Wout_max, Win_max. Therefore, inorder to ensure the input/output performance of the battery pack 10, thetarget temperature Ktarg is set to a value between the temperatures Kb1,Kb2. The target temperature Ktarg may be set to any temperature asneeded as long as the temperature falls between the temperatures Kb1,Kb2.

When the temperatures Kb of the plurality of single cells 11 aredetected and there are variations among these temperatures Kb, theaverage value of these temperatures Kb may be compared with the targettemperature Ktarg or the lowest temperature Kb or the highesttemperature Kb may be compared with the target temperature Ktarg.

In the process of step S112, when the battery temperature Kb is lowerthan the target temperature Ktarg, the controller 30 determines that itis required to heat the battery pack 10, and executes the process ofstep S113. The process from step S113 is the process of heating thebattery pack 10. When there are variations among the temperatures Kb ofthe plurality of single cells 11, the average value of the temperaturesKb or the lowest temperature Kb may be compared with the targettemperature Ktarg. When the average value or the lowest temperature Kbis lower than the target temperature Ktarg, the controller 30 determinesthat it is required to heat the battery pack 10.

In the process of step S112, when the battery temperature Kb is higherthan or equal to the target temperature Ktarg, the controller 30determines that it is required to cool the battery pack 10, and executesthe process of step S119. The process from step S119 is the process ofcooling the battery pack 10. When there are variations among thetemperatures Kb of the plurality of single cells 11, the average valueof the temperatures Kb or the highest temperature Kb may be comparedwith the target temperature Ktarg. When the average value or the highesttemperature Kb is higher than the target temperature Ktarg, thecontroller 30 determines that it is required to cool the battery pack10.

Initially, the process of heating the battery pack 10 will be described.

The controller 30 initiates the process of heating the battery pack 10(heating process) in step S113. Specifically, the controller 30 operatesthe temperature adjustment device 41 in order to increase thetemperature Kb of the battery pack 10. In step S114, the controller 30calculates the SOC of the battery pack 10, and determines in step S115whether the calculated SOC is higher than or equal to the target valueSOC_targ. When the calculated SOC is higher than or equal to the targetvalue SOC_targ, the controller 30 executes the process of step S109shown in FIG. 3. When the controller 30 has proceeded from the processof step S115 to the process of step S109, the controller 30 completesexternal charging, and also completes the heating process. When thecalculated SOC is lower than the target value SOC_targ, the controller30 executes the process of step S116.

In step S116, the controller 30 detects the temperature Kb of thebattery pack 10 on the basis of the output of the temperature sensor 21.In step S117, the controller 30 determines whether the batterytemperature Kb detected in the process of step S116 is higher than orequal to the target temperature Ktarg. The target temperature Ktarg thatis used in the process of step S117 is the same as the targettemperature Ktarg that is used in the process of step S112.

When the battery temperature Kb is lower than the target temperatureKtarg, the controller 30 returns to the process of step S114. When thecontroller 30 has returned to the process of step S114, the controller30 continues the heating process and external charging. When the batterytemperature Kb is higher than or equal to the target temperature Ktarg,the controller 30 completes the heating process in step S118, andreturns to the process of step S111. With the processes of step S113 tostep S118, it is possible to cause the SOC of the battery pack 10 toreach the target value SOC_targ by the charging completion time Te. Whenthe SOC of the battery pack 10 reaches the target value SOC_targ orbefore the SOC of the battery pack 10 reaches the target value SOC_targ,it is possible to cause the battery temperature Kb to reach the targettemperature Ktarg.

Next, the process of cooling the battery pack 10 will be described.

The controller 30 initiates the process of cooling the battery pack 10(cooling process) in step S119. Specifically, the controller 30 operatesthe temperature adjustment device 41 in order to reduce the temperatureKb of the battery pack 10. The controller 30 calculates the SOC of thebattery pack 10 in step S120, and determines in step S121 whether thecalculated SOC is higher than or equal to the target value SOC_targ.When the calculated SOC is higher than or equal to the target valueSOC_targ, the controller 30 executes the process of step S109 shown inFIG. 3. When the controller 30 has proceeded from the process of stepS121 to the process of step S109, the controller 30 completes externalcharging, and also completes the cooling process. When the calculatedSOC is lower than the target value SOC_targ, the controller 30 executesthe process of step S122.

In step S122, the controller 30 detects the temperature Kb of thebattery pack 10 on the basis of the output of the temperature sensor 21.In step S123, the controller 30 determines whether the batterytemperature Kb detected in the process of step S122 is lower than orequal to the target temperature Ktarg. The target temperature Ktarg isthe same as the target temperature Ktarg described in the process ofstep S112. When the battery temperature Kb is higher than the targettemperature Ktarg, the controller 30 returns to the process of stepS120.

When the controller 30 has returned to the process of step S120, thecontroller 30 continues the cooling process and external charging. Whenthe battery temperature Kb is lower than or equal to the targettemperature Ktarg, the controller 30 completes the cooling process instep S124, and returns to the process of step S111. With the processesof step S119 to step S124, it is possible to cause the SOC of thebattery pack 10 to reach the target value SOC_targ by the chargingcompletion time Te. When the SOC of the battery pack 10 reaches thetarget value SOC_targ or before the SOC of the battery pack 10 reachesthe target value SOC_targ, it is possible to cause the batterytemperature Kb to reach the target temperature Ktarg.

Next, the process after completion of external charging will bedescribed with reference to the flowchart shown in FIG. 6 to FIG. 8. Theprocess shown in FIG. 6 to FIG. 8 is executed by the controller 30. Theprocess shown in FIG. 6 to FIG. 8 is initiated at the time when theprocess shown in FIG. 4 is executed.

In step S201, the controller 30 stores information about the temperatureadjustment process during external charging in the memory 31. Thetemperature adjustment process includes the heating process (S113 toS118) and the cooling process (S119 to S124), described in the processshown in FIG. 4.

In step S202, the controller 30 acquires current time Tc from the clock32. In step S203, the controller 30 acquires the midnight ratetermination time TMe on the basis of the information input through theinput unit 34. In step S204, the controller 30 determines whether thecurrent time Tc is later than or equal to the midnight rate terminationtime TMe. The current time Tc and the midnight rate termination time TMeare respectively obtained in the processes of step S202 and step S203.

When the current time Tc is later than the midnight rate terminationtime TMe, the controller 30 completes the process shown in FIG. 6 toFIG. 8. On the other hand, when the current time Tc is earlier than themidnight rate termination time TMe, the controller 30 acquires theoperation-starting time TU, input from the input unit 34, in step S205.In step S206, the controller 30 determines whether theoperation-starting time TU is later than the midnight rate terminationtime TMe. When the operation-starting time TU is earlier than or equalto the midnight rate termination time TMe, the controller 30 executesthe process of step S207. On the other hand, when the operation-startingtime TU is later than the midnight rate termination time TMe, thecontroller 30 executes the process of step S210.

In step S207, the controller 30 detects the temperature Kb of thebattery pack 10 on the basis of the output of the temperature sensor 21.In step S208, the controller 30 adjusts the temperature of the batterypack 10 on the basis of the battery temperature Kb detected in theprocess of step S207. Specifically, when the battery temperature Kb islower than the target temperature Ktarg, the controller 30 brings thebattery temperature Kb close to the target temperature Ktarg through theheating process caused by the operation of the temperature adjustmentdevice 41. On the other hand, when the battery temperature Kb is higherthan the target temperature Ktarg, the controller 30 brings the batterytemperature Kb close to the target temperature Ktarg through the coolingprocess caused by the operation of the temperature adjustment device 41.When the battery temperature Kb is the target temperature Ktarg, neitherthe heating process nor the cooling process is executed. When thetemperature adjustment device 41 is operated, electric power from thecommercial power supply 28 is used.

In step S209, the controller 30 acquires the current time Tc from theclock 32, and determines whether the current time Tc is later than orequal to the operation-starting time TU. When the current time Tc islater than or equal to the operation-starting time TU, the controller 30completes the process shown in FIG. 6 to FIG. 8. On the other hand, whenthe current time Tc is earlier than the operation-starting time TU, thecontroller 30 returns to the process of step S207. When theoperation-starting time TU is earlier than or equal to the midnight ratetermination time TMe, it is possible to cause the battery temperature Kbat the operation-starting time TU to reach the target temperature Ktargthrough the processes of step S207 to step S209.

When the controller 30 has proceeded from the process of step S206 tothe process of step S210, the controller 30 calculates a time ΔTrbetween the operation-starting time TU and the midnight rate terminationtime TMe. In step S211, the controller 30 calculates a variation ΔKb inthe battery temperature Kb. The temperature variation ΔKb is a variationin the battery temperature Kb in the period from the midnight, ratetermination time TMe to the operation-starting time TU. Specifically,the temperature variation ΔKb indicates a value obtained by subtractingthe battery temperature Kb of the midnight rate termination time TMefrom the battery temperature Kb of the operation-starting time TU.

In the present embodiment, as will be described later, the temperatureof the battery pack 10 is adjusted until the midnight rate terminationtime TMe; however, the temperature of the battery pack 10 is notadjusted after the midnight rate termination time TMe. Therefore, thetemperature variation ΔKb in the period between the midnight ratetermination time TMe and the operation-starting time TU depends on theoutside air temperature Ke, and it is possible to estimate thetemperature variation ΔKb on the basis of the outside air temperatureKe.

Specifically, the temperature variation ΔKb may be calculated on thebasis of the following mathematical expression (1).

$\begin{matrix}{{\Delta \; {Kb}} = \frac{Q \times \Delta \; {Tr}}{Cp}} & (1)\end{matrix}$

In the above mathematical expression (1), Q (in watts (W)) is the heatradiation amount or heat receiving amount of the battery pack 10. Theamount of heat Q is calculated on the basis of the battery temperatureKb and the outside air temperature Ke. That is, it is possible tocalculate the amount of heat Q by detecting the battery temperature Kband the outside air temperature Ke. When the battery temperature Kb ishigher than the outside air temperature Ke, heat of the battery pack 10is released to the air. Therefore, it is possible to calculate the heatradiation amount Q on the basis of the difference between the batterytemperature Kb and the outside air temperature Ke. For example, when thecorrelation between the heat radiation amount Q and the differencebetween the battery temperature Kb and the outside air temperature Ke isprepared as a map or an arithmetic expression, it is possible tocalculate the heat radiation amount Q from the difference between thebattery temperature Kb and the outside air temperature Ke.

On the other hand, when the battery temperature Kb is lower than theoutside air temperature Ke, the battery pack 10 receives heat from theair. Therefore, it is possible to calculate the heat receiving amount Qon the basis of the difference between the battery temperature Kb andthe outside air temperature Ke. For example, when the correlationbetween the heat receiving amount Q and the difference between thebattery temperature Kb and the outside air temperature Ke is prepared asa map or an arithmetic expression, it is possible to calculate the heatreceiving amount Q from the difference between the battery temperatureKb and the outside air temperature Ke.

In the present embodiment, the heat radiation amount Q is defined as apositive value, and the heat receiving amount Q is defined as a negativevalue. Therefore, when the heat radiation amount Q is calculated, thetemperature variation ΔKb becomes a positive value. When the heatreceiving amount Q is calculated, the temperature variation ΔKb becomesa negative value. When the temperature variation ΔKb is a positivevalue, the battery temperature Kb increases in the period from themidnight rate termination time TMe to the operation-starting time. TU.When the temperature variation ΔKb is a negative value, the batterytemperature Kb decreases in the period from the midnight ratetermination time TMe to the operation-starting time TU.

In the above mathematical expression (1), Cp is the heat capacity (inJ/° C.) of the battery pack 10. The heat capacity Cp may be measured inadvance by an experiment, or the like. Information about the heatcapacity Cp (information that specifies the heat capacity Cp) may bestored in the memory 31. In the above mathematical expression (1), ΔTris a time calculated in the process of step S210.

In step S212, the controller 30 calculates a corrected temperatureKcorr. Specifically, the corrected temperature Kcorr is calculated onthe basis of the following mathematical expression (2). In the followingmathematical expression (2), Ktarg is the target temperature describedin the process shown in FIG. 4, and ΔKb is the temperature variationcalculated in the process of step S211.

Kcorr=Ktarg+ΔKtb  (2)

In step S213, the controller 30 loads the information about thetemperature adjustment process, stored in the memory 31. The informationabout the temperature adjustment process is information stored in thememory 31 in the process of step S201. In step S214, the controller 30determines whether the temperature adjustment process loaded in theprocess of step S213 is the heating process. When the loaded temperatureadjustment process is the heating process, the controller 30 executesthe process of step S215 shown in FIG. 7. On the other hand, when theloaded temperature adjustment process is the cooling process, thecontroller 30 executes the process of step S220 shown in FIG. 8.

In step S215, the controller 30 detects the battery temperature Kb onthe basis of the output of the temperature sensor 21. In step S216, thecontroller 30 determines whether the battery temperature Kb detected inthe process of step S215 is higher than or equal to the correctedtemperature Kcorr. The value calculated in the process of step S212shown in FIG. 6 is used as the corrected temperature Kcorr.

When the controller 30 proceeds from the process of step S214 shown inFIG. 6 to the process of step S215 shown in FIG. 7, the controller 30has determined that the heating process has been executed duringexternal charging. When the heating process has been executed duringexternal charging, the battery temperature Kb tends to be higher thanthe outside air temperature Ke, and Q shown in the above-describedmathematical expression (1) becomes the heat radiation amount.Therefore, the temperature variation ΔKb becomes a positive value, andthe corrected temperature Kcorr is higher than the target temperatureKtarg by the temperature variation ΔKb.

When the battery temperature Kb is lower than the corrected temperatureKcorr, the controller 30 executes the process of step S217. On the otherhand, when the battery temperature Kb is higher than or equal to thecorrected temperature Kcorr, the controller 30 executes the process ofstep S218. In step S217, the controller 30 executes the heating processby operating the temperature adjustment device 41. By executing theheating process, it is possible to cause the battery temperature Kb toreach the corrected temperature Kcorr by increasing the batterytemperature Kb. After the process of step S217, the controller 30returns to the process of step S215. In step S218, the controller 30acquires the current time Tc from the clock 32.

In step S219, the controller 30 determines whether the current time Tcacquired in the process of step S218 is later than or equal to themidnight rate termination time TMe. When the current time Tc is laterthan or equal to the midnight rate termination time TMe, the controller30 completes the process shown in FIG. 6 to FIG. 8. On the other hand,when the current time Tc is earlier than the midnight rate terminationtime TMe, the controller 30 returns to the process of step S215.

In step S220 shown in FIG. 8, the controller 30 detects the batterytemperature Kb on the basis of the output of the temperature sensor 21.In step S221, the controller 30 determines whether the batterytemperature Kb detected in the process of step S220 is lower than orequal to the corrected temperature Kcorr. The value calculated in theprocess of step S212 shown in FIG. 6 is used as the correctedtemperature Kcorr. When the controller 30 proceeds from the process ofstep S214 shown in FIG. 6 to the process of step S220 shown in FIG. 8,the controller 30 has determined that the cooling process has beenexecuted during external charging. When the cooling process has beenexecuted during external charging, the battery temperature Kb tends tobe lower than the outside air temperature Ke, and Q shown in theabove-described mathematical expression (1) becomes the heat receivingamount. Therefore, the temperature variation. ΔKb becomes a negativevalue, and the corrected temperature Kcorr is lower than the targettemperature Ktarg by the temperature variation ΔKb.

When the battery temperature Kb is higher than the corrected temperatureKcorr, the controller 30 executes the process of step S222. When thebattery temperature Kb is lower than or equal to the correctedtemperature Kcorr, the controller 30 executes the process of step S223.In step S222, the controller 30 executes the cooling process byoperating the temperature adjustment device 41. By executing the coolingprocess, it is possible to cause the battery temperature Kb to reach thecorrected temperature Kcorr by reducing the battery temperature Kb.After the process of step S222, the controller 30 returns to the processof step S220. In step S223, the controller 30 acquires the current timeTc from the clock 32.

In step S224, the controller 30 determines whether the current time Tcacquired in the process of step S223 is later than or equal to themidnight rate termination time TMe. When the current time Tc is laterthan or equal to the midnight rate termination time TMe, the controller30 completes the process shown in FIG. 6 to FIG. 8. On the other hand,when the current time Tc is earlier than the midnight rate terminationtime TMe, the controller 30 returns to the process of step S220.

FIG. 9 shows a change in the battery temperature Kb in winter, or thelike. In FIG. 9, the ordinate axis represents battery temperature Kb,and the abscissa axis represents time. In the example shown in FIG. 9, aperiod during which the vehicle is traveling, a period during whichexternal charging is being carried out and a period during which theheating process is being executed are shown. In the period during whichexternal charging is being carried out, the heating process is alsobeing executed.

The charging completion time Te and the operation-starting time TU areset by the user, and the charging completion time Te and theoperation-starting time TU are set earlier than the midnight rateinitial time TMs. The charging completion time Te is earlier than themidnight rate termination time TMe. The operation-starting time TU islater than the midnight rate termination time TMe.

In FIG. 9, in the period during which the vehicle is not traveling, thebattery temperature Kb is decreasing because the battery pack 10receives thermal influence from the surrounding environment. That is,because the outside air temperature Ke is lower than the batterytemperature Kb, the battery temperature Kb is decreasing upon receptionof the influence of the outside air temperature Ke. In the period duringwhich the vehicle is traveling, a decrease in the battery temperature Kbis suppressed by adjusting the temperature of the battery pack 10.

In FIG. 9, because the heating process is also being executed at thetime when external charging is carried out, the battery temperature Kbincreases. With the process shown in FIG. 4, it is possible to cause thebattery temperature Kb to reach the target temperature Ktarg by thecharging completion time Te, in other words, by the time when externalcharging completes. In the example shown in FIG. 9, after passage of thecharging completion time Te as well, the heating process is executed onthe basis of the process shown in FIG. 6 and FIG. 7 until the midnightrate termination time TMe, and the battery temperature Kb is increasedto the corrected temperature Kcorr. When the heating process is stoppedat the midnight rate termination time TMe, the battery temperature Kbdecreases in response to the outside air temperature Ke, and this amountof decrease becomes ΔKb.

Because the corrected temperature Kcorr is higher than the targettemperature Ktarg by the temperature variation ΔKb, even when thebattery temperature Kb decreases, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Ktarg. If the heating process is stopped at the chargingcompletion time Te shown in FIG. 9, the battery temperature Kb continuesto decrease as indicated by the dashed line in FIG. 9 upon reception ofthe influence of the outside air temperature Ke. As a result, thebattery temperature Kb at the operation-starting time TU becomes lowerthan the target temperature Ktarg.

If the battery temperature Kb at the operation-starting time TU becomeslower than the target temperature Ktarg, it becomes difficult to ensurethe input/output performance of the battery pack 10 at the time ofinitiating a start-up of the vehicle at the operation-starting time TU.In the present embodiment, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Ktarg, so it is possible to prevent the battery temperatureKb from being lower than the target temperature Ktarg. Thus, at theoperation-starting time TU, it is possible to ensure the input/outputperformance of the battery pack 10.

FIG. 10 shows a change in the battery temperature Kb in summer, or thelike. In FIG. 10, the ordinate axis represents battery temperature Kb,and the abscissa axis represents time. In the example shown in FIG. 10,a period during which the vehicle is traveling, a period during whichexternal charging is being carried out and a period during which thecooling process is being executed are shown. In the period during whichexternal charging is being carried out, the cooling process is alsobeing executed.

The charging completion time Te and the operation-starting time TU areset by the user, and the charging completion time Te and theoperation-starting time TU are set earlier than the midnight rateinitial time TMs. The charging completion time Te is earlier than themidnight rate termination time TMe. The operation-starting time TU islater than the midnight rate termination time TMe.

In FIG. 10, in the period during which the vehicle is not traveling, thebattery temperature Kb is increasing because the battery pack 10receives thermal influence from the surrounding environment. That is,because the outside air temperature Ke is higher than the batterytemperature Kb, the battery temperature Kb is increasing upon receptionof the influence of the outside air temperature Ke. In the period duringwhich the vehicle is traveling, an increase in the battery temperatureKb is suppressed by adjusting the temperature of the battery pack 10.

In FIG. 10, because the cooling process is also being executed whenexternal charging is carried out, the battery temperature Kb decreases.With the process shown in FIG. 4, it is possible to cause the batterytemperature Kb to reach the target temperature Ktarg by the chargingcompletion time Te, in other words, by the time when external chargingcompletes. In the example shown in FIG. 10, after passage of thecharging completion time Te as well, the cooling process is executed onthe basis of the process shown in FIG. 6 and FIG. 8 until the midnightrate termination time TMe, and the battery temperature Kb is reduced tothe corrected temperature Kcorr.

Because the corrected temperature Kcorr is lower than the targettemperature Ktarg by the temperature variation ΔKb, even when thebattery temperature Kb increases upon reception of the influence of theoutside air temperature Ke after the midnight rate termination time TMe,it is possible to bring the battery temperature Kb at theoperation-starting time TU to the target temperature Ktarg. If thecooling process is stopped after the charging completion time Te shownin FIG. 10, the battery temperature Kb continues to increase uponreception of the influence of the outside air temperature Ke asindicated by the dashed line in FIG. 10. As a result, the batterytemperature Kb at the operation-starting time TU becomes higher than thetarget temperature Ktarg.

If the battery temperature Kb at the operation-starting time TU becomeshigher than the target temperature Ktarg, it may be difficult to ensurethe input/output performance of the battery pack 10 at the time ofinitiating a start-up of the vehicle at the operation-starting time TU.

In the present embodiment, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Ktarg, so it is possible to prevent the battery temperatureKb from being higher than the target temperature Ktarg. Thus, at theoperation-starting time TU, it is possible to ensure the input/outputperformance of the battery pack 10.

According to FIG. 9 and FIG. 10, electric power in the midnight timeperiod is used to carry out external charging or executing thetemperature adjustment process of the battery pack 10. The cost ofelectricity of the midnight time period is lower than the cost ofelectricity of a time period other than the midnight time period.Therefore, it is possible to reduce the cost of electricity at the timeof carrying out external charging or executing the temperatureadjustment process.

On the other hand, because the temperature adjustment process of thebattery pack 10 is not carried out at the midnight rate termination timeTMe or later, if the operation-starting time TU is later than themidnight rate termination time TMe, the battery temperature Kb maychange in the period from the midnight rate termination time TMe to theoperation-starting time TU. Specifically, the battery temperature Kb mayincrease or decrease in response to the temperature of the surroundingenvironment of the battery pack 10 (outside air temperature Ke).Therefore, in the present embodiment, the corrected temperature Kcorr isset in consideration of the heat radiation amount or heat receivingamount of the battery pack 10 in the period from the midnight ratetermination time TMe to the operation-starting time TU.

When the battery temperature Kb at the midnight rate termination timeTMe is caused to reach the corrected temperature Kcorr, it is possibleto bring the battery temperature Kb at the operation-starting time TU tothe target temperature Ktarg. For example, when the battery temperatureKb decreases in the period from the midnight rate termination time TMeto the operation-starting time TU, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Ktarg by causing the battery temperature Kb at the midnightrate termination time TMe to be higher than the target temperature Ktargby the temperature variation ΔKb.

On the other hand, when the battery temperature Kb increases in theperiod from the midnight rate termination time TMe to theoperation-starting time TU, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Ktarg by causing the battery temperature Kb at the midnightrate termination time TMe to be lower than the target temperature Ktargby the temperature variation ΔKb. Thus, at the time of initiating astart-up of the vehicle, it is possible to bring the battery temperatureKb to the target temperature Ktarg, so it is possible to ensure theinput/output performance of the battery pack 10 at the time of astart-up of the vehicle.

In order to bring the battery temperature Kb at the operation-startingtime TU to the target temperature Ktarg, it is conceivable to executethe temperature adjustment process (the heating process or the coolingprocess) by the operation-starting time TU as in the case of first andsecond comparative embodiments shown in FIG. 9 and FIG. 10. If thetemperature adjustment process is executed in the period from theinitiation of external charging to the operation-starting time TU as inthe case of the first comparative embodiment, electric power from thecommercial power supply 28 is used at a rate higher than the midnightcost of electricity also in the period between the midnight ratetermination time TMe and the operation-starting time TU. Thus, in thefirst comparative embodiment, a cost of electricity required for thetemperature adjustment process increases as compared to the presentembodiment.

If the temperature adjustment process is executed in the period from thecharging completion time Te to the operation-starting time TU as in thecase of the second comparative embodiment, electric power from thecommercial power supply 28 is used at a rate higher than the midnightcost of electricity in the period between the midnight rate terminationtime TMe and the operation-starting time TU. If the duration of thetemperature adjustment process according to the second comparativeembodiment is longer than or equal to the duration of the temperatureadjustment process according to the present embodiment, a cost ofelectricity required for the temperature adjustment process increases inthe second comparative embodiment as compared to the present embodiment.If the duration of the temperature adjustment process according to thesecond comparative embodiment is shorter than the duration of thetemperature adjustment process according to the present embodiment, alarger amount of electric power should be used in order to bring thebattery temperature Kb to the target temperature Ktarg. Thus, in thesecond comparative embodiment, a cost of electricity required for thetemperature adjustment process tends to be higher than that of thepresent embodiment.

In the present embodiment, the target temperature Ktarg is set to aspecific temperature; however, the target temperature Ktarg is notlimited to this configuration. Specifically, instead of the targettemperature Ktarg, it is possible to set a specific temperature range(referred to as target temperature range). In this case, it is possibleto execute the temperature adjustment process of the battery pack 10such that the temperature Kb of the battery pack 10 falls within thetarget temperature range. When the target temperature range is set, anupper limit value and a lower limit value are set, and the range betweenthe upper limit value and the lower limit value becomes the targettemperature range.

In the process shown in FIG. 4, when the battery temperature Kb is lowerthan the lower limit vale of the target temperature range, the heatingprocess may be executed. Specifically, it is possible to set the lowerlimit value of the target temperature range as the target temperatureKtarg described in the processes of step S112 and step S117. On theother hand, at the time of executing the process shown in FIG. 4, whenthe battery temperature Kb is higher than the upper limit value of thetarget temperature range, the cooling process may be executed.Specifically, it is possible to set the upper limit value of the targettemperature range as the target temperature Ktarg described in theprocesses of step S112 and step S123.

In the process shown in FIG. 6 to FIG. 8, when the heating process isexecuted at the charging completion time Te or later, a temperatureobtained by adding the temperature variation ΔKb to the upper limitvalue of the target temperature range may be set as the correctedtemperature Kcorr. When the heating process is executed in the periodfrom the charging completion time Te to the midnight rate terminationtime TMe, the battery temperature Kb tends to decrease at the midnightrate termination time TMe or later. When the corrected temperature Kcorris set to a temperature higher than the upper limit value of the targettemperature range by the temperature variation ΔKb, it is possible tobring the battery temperature Kb at the operation-starting time TU tothe upper limit value of the target temperature range. Even when thebattery temperature Kb is easy to decrease and the actual temperaturevariation ΔKb becomes larger than the estimated temperature variationΔKb, it is possible to bring the battery temperature Kb at theoperation-starting time TU into the target temperature range.

On the other hand, when the cooling process is executed at the chargingcompletion time Te or later, a temperature obtained by subtracting thetemperature variation ΔKb from the lower limit value of the targettemperature range may be set as the corrected temperature Kcorr. Whenthe cooling process is executed in the period from the chargingcompletion time Te to the midnight rate termination time TMe, thebattery temperature Kb tends to increase at the midnight ratetermination time TMe or later. If the corrected temperature Kcorr is setto a temperature lower than the lower limit value of the targettemperature range by the temperature variation ΔKb, it is possible tobring the battery temperature Kb at the operation-starting time TU tothe lower limit value of the target temperature range. Even when thebattery temperature Kb is easy to increase and the actual temperaturevariation ΔKb becomes larger than the estimated temperature variationΔKb, it is possible to bring the battery temperature Kb at theoperation-starting time TU into the target temperature range.

It is possible to set the corrected temperature Kcorr in considerationof an upper limit temperature that is allowed in the battery pack 10(referred to as allowable upper limit temperature). The allowable upperlimit temperature is a temperature for protecting the battery pack 10from excessive heat generation. When the corrected temperature Kcorr ishigher than the allowable upper limit temperature, the battery pack 10excessively generates heat because of the heating process at thecharging completion time Te or later. Therefore, when the correctedtemperature Kcorr is higher than the allowable upper limit temperature,it is possible to set the allowable upper limit temperature as thecorrected temperature Kcorr that is used in the process of step S216shown in FIG. 7. The allowable upper limit temperature may be set inadvance, and information about the allowable upper limit temperature(information that specifies the allowable upper limit temperature) maybe stored in the memory 31.

The charging completion time Te is set by the user. When the chargingcompletion time Te is included in the midnight time period, it ispossible to carry out external charging with electric power of themidnight time period. A user who considers the midnight time period mayset the time included in the midnight time period as the chargingcompletion time Te.

On the other hand, some users may set the charging completion time Tewithout consideration of the midnight time period. For example, the setcharging completion time Te may be later than the midnight ratetermination time TMe. In this case, when it is possible to completeexternal charging by the midnight rate termination time TMe, it ispossible to complete external charging by the midnight rate terminationtime TMe. Thus, it is possible to carry out eternal charging bysufficiently utilizing electric power from the commercial power supply28 in the midnight time period, so it is possible to reduce a cost ofelectricity required to carry out external charging.

However, external charging may be completed after the midnight ratetermination time TMe. Specifically, when the charging completion time Teis later than the midnight rate termination time TMe, it is possible tocomplete external charging at any time in the period from the midnightrate termination time TMe to the charging completion time Te. In thiscase, external charging is carried out in the midnight time period andthe time period other than the midnight time period. When the durationof external charging in the midnight time period is longer than theduration of external charging in the time period other than the midnighttime period, it is possible to carry out external charging by activelyusing electric power from the commercial power supply 28 in the midnighttime period. Thus, it is easy to reduce a cost of electricity requiredto carry out external charging.

However, when external charging is carried out even at the midnight ratetermination time TMe or later, as a time from the midnight ratetermination time TMe until external charging is completed extends, theduration of external charging extends in the time period other than themidnight time period. In this case, a cost of electricity required tocarry out external charging tends to increase. Therefore, as describedabove, when the duration of external charging in the midnight timeperiod is extended as compared to the duration of external charging inthe time period other than the midnight time period, it is possible tosuppress an increase in cost of electricity required to carry outexternal charging.

On the other hand, when the time at which the charging completion timeTe is set is earlier than the midnight rate initial time TMs, it ispossible to carry out external charging not only in the midnight timeperiod but also in the time period other than the midnight time period.In this case as well, as described above, when the duration of externalcharging in the midnight time period is extended as compared to theduration of external charging in the time period other than the midnighttime period, it is possible to suppress an increase in cost ofelectricity required to carry out external charging.

In order to actively utilize electric power from the commercial powersupply 28 in the midnight time period, the percentage of the duration ofexternal charging in the midnight time period (referred to as firstcharging percentage) just needs to be increased as compared to thepercentage of the duration of external charging in the time period otherthan the midnight time period (referred to as second chargingpercentage). The first charging percentage is a value obtained bydividing the duration of external charging in the midnight time periodby the total time of the midnight time period. The second chargingpercentage is a value obtained by dividing the duration of externalcharging in the time period other than the midnight time period by thetotal time of the time period other than the midnight time period.Specifically, external charging just needs to be carried out such thatthe above-described condition of the percentages (the first chargingpercentage and the second charging percentage) in consideration of atime period from the time at which the charging completion time Te hasbeen set to the charging completion time Te.

The controller 30 is able to carry out external charging on the basis ofthe process shown in FIG. 11. The process shown in FIG. 11 is to specifythe duration of external charging at the time of carrying out externalcharging on the basis of the process shown in FIG. 4. The process shownin FIG. 11 is initiated at the time when the charging completion time Tehas been set.

In step S301 shown in FIG. 11, the controller 30 acquires the currenttime Tc, the charging completion time Te, the midnight rate initial timeTMs and the midnight rate termination time TMe. Here, the current timeTc is the time at which the charging completion time Te has been set. Instep S302, the controller 30 determines whether (at least part of) themidnight time period is included within the period from the current timeTc to the charging completion time Te.

The case where the midnight time period is included within the periodfrom the current time Tc to the charging completion time Te includesfour cases (FIG. 12A to FIG. 12D) as shown in FIG. 12A to FIG. 12D. Inthe case shown in FIG. 12A, the midnight time period is included withinthe period from the current time Tc to the charging completion time Te,and the midnight time period is longer than or equal to a time from thecurrent time Tc to the charging completion time Te. In the case shown inFIG. 12B, the entire midnight time period is included within the periodfrom the current time Tc to the charging completion time Te. Themidnight rate initial time TMs is later than the current time Tc, andthe midnight rate termination time TMe is earlier than the chargingcompletion time Te.

In the case shown in FIG. 12C, part of the midnight time period isincluded within the period from the current time Tc to the chargingcompletion time Te, and the midnight rate termination time TMe isincluded in the period between the current time Tc and the chargingcompletion time Te. In the case shown in FIG. 12D, part of the midnighttime period is included within the period from the current time Tc tothe charging completion time Te, and the midnight rate initial time TMsis included in the period between the current time Tc and the chargingcompletion time Te.

When no midnight time period is included (even at least part of themidnight time period is not included) within the period from the currenttime Tc to the charging completion time Te, the controller 30 carriesout external charging by, using the time period other than the midnighttime period in step S303. When (at least part of) the midnight timeperiod is included within the period from the current time Tc to thecharging completion time Te, the controller 30 determines in step S304whether it is possible to initiate and complete external charging withinthe midnight time period.

In the process of step S304, by acquiring the processing time ΔTp, thecharging completion time Te, the midnight rate initial time TMs and themidnight rate termination time TMe, it is possible to determine whetherit is possible to initiate and complete external charging within themidnight time period. In the case shown in FIG. 12A, it is possible toinitiate and complete external charging within the midnight time period.In the case shown in FIG. 12B, when the processing time ΔTp is includedwithin the midnight time period, it is possible to initiate and completeexternal charging within the midnight time period.

In the case shown in FIG. 12C, when the processing time ΔTp is includedwithin the period between the current time Tc and the midnight ratetermination time TMe, it is possible to initiate and complete externalcharging within the midnight time period. In the case shown in FIG. 12D,when the processing time ΔTp is included within the period between themidnight rate initial time TMs and the charging completion time Te, itis possible to initiate and complete external charging within themidnight time period. When it is possible to initiate and completeexternal charging within the midnight time period, the controller 30carries out external charging within the midnight time period in stepS305.

When it is not possible to initiate and complete external chargingwithin the midnight time period, the controller 30 carries out externalcharging in the midnight time period in step S306. It is not possible tocause the SOC of the battery pack 10 to reach the target value SOC_targonly by carrying out external charging in the midnight time period, andan insufficient amount of charge remains. Therefore, in order tocompensate for the insufficient amount of charge, external charging isalso carried out in the time period other than the midnight time period.

When the process of step S306 is executed in the case shown in FIG. 12B,external charging is carried out by using the entire midnight timeperiod, and external charging is carried out by also using the timeperiod other than the midnight time period. When external charging iscarried out in the time period other than the midnight time period,external charging may be carried out earlier than the midnight rateinitial time TMs or external charging may be carried out later than themidnight rate termination time TMe. That is, external charging justneeds to be completed by the charging completion time Te.

In the case shown in FIG. 12C, external charging is carried out in themidnight time period from the current time Tc to the midnight ratetermination time TMe, and external charging is also carried out laterthan the midnight rate termination time TMe. In the case shown in FIG.12D, external charging is carried out in the midnight time period fromthe midnight rate initial time TMs to the charging completion time Te,and external charging is also carried out earlier than the midnight rateinitial time TMs.

External charging is carried out by sufficiently utilizing the midnighttime period, and external charging is also carried out in the timeperiod other than the midnight time period in order to compensate for aninsufficient amount of charge. Thus, as described above, it is possibleto cause the first charging percentage to be higher than the secondcharging percentage. Thus, a cost of electricity required to carry outexternal charging is easy to be reduced.

In the present embodiment, the user sets the charging completion time Teand the operation-starting time TU; however, setting of the chargingcompletion time Te and the operation-starting time TU is not limited tothis configuration. That is, the user is allowed to set only theoperation-starting time TU without setting the charging completion timeTe. In this case, external charging just needs to be completed by theoperation-starting time TU, and the time at which external charging iscompleted may be set as needed. That is, the time at which externalcharging is completed is earlier than or equal to the operation-startingtime TU. It is possible to carry out external charging on the basis ofthe thus set external charging completion time as in the case of thepresent embodiment.

On the other hand, the operation-starting time TU is set by the user.When the operation-starting time TU is later than the midnight ratetermination time TMe, it is possible to execute the temperatureadjustment process (the heating process or the cooling process) for thebattery pack 10 by operating the temperature adjustment device 41 untilthe midnight rate termination time TMe as shown in FIG. 9 and FIG. 10.Thus, it is possible to operate the temperature adjustment device 41 byusing only electric power from the commercial power supply 28 in themidnight time period, so it is possible to reduce a cost of electricityrequired to operate the temperature adjustment device 41.

However, the temperature adjustment process may be completed later thanthe midnight rate termination time TMe. Specifically, it is possible tocomplete the temperature adjustment process at any time in the periodbetween the midnight rate termination time TMe and theoperation-starting time TU. In this case, the temperature adjustmentprocess is executed in the midnight time period and in the time periodother than the midnight time period. When the duration of executing thetemperature adjustment process in the midnight time period is longerthan the duration of executing the temperature adjustment process in thetime period other than the midnight time period, it is possible toexecute the temperature adjustment process by actively using electricpower from the commercial power supply 28 in the midnight time period.Thus, it becomes easy to reduce a cost of electricity required tooperate the temperature adjustment device 41.

When the temperature adjustment process is executed at the midnight ratetermination time TMe or later, as a time from the midnight ratetermination time TMe to completion of the temperature adjustment processextends, the duration of executing the temperature adjustment processextends in the time period other than the midnight time period. In thiscase, a cost of electricity required to operate the temperatureadjustment device 41 tends to increase. Therefore, as described above,when the duration of executing the temperature adjustment process in themidnight time period is extended as compared to the duration ofexecuting the temperature adjustment process in the time period otherthan the midnight time period, it is possible to suppress an increase incost of electricity required to operate the temperature adjustmentdevice 41.

On the other hand, the temperature adjustment process may be executedearlier than the midnight rate initial time TMs, in other words, in thetime period other than the midnight time period. In this case as well,as described above, when the duration of executing the temperatureadjustment process in the midnight time period is extended as comparedto the duration of executing the temperature adjustment process in thetime period other than the midnight time period, it is possible tosuppress an increase in cost of electricity required to execute thetemperature adjustment process.

In order to actively utilize electric power from the commercial powersupply 28 in the midnight time period, the percentage of the duration ofexecuting the temperature adjustment process in the midnight time periodjust needs to be increased as compared to the percentage of the durationof executing the temperature adjustment process in the time period otherthan the midnight time period. Hereinafter, the percentage of theduration of executing the temperature adjustment process in the midnighttime period is referred to as first adjustment percentage. Thepercentage of the duration of executing the temperature adjustmentprocess in the time period other than the midnight time period isreferred to as second adjustment percentage. The first adjustmentpercentage is a value obtained by dividing the duration of executing thetemperature adjustment process in the midnight time period by the totaltime of the midnight time period. The second adjustment percentage is avalue obtained by dividing the duration of executing the temperatureadjustment process in the time period other than the midnight timeperiod by the total time in the time period other than the midnight timeperiod. Specifically, the temperature adjustment process just needs tobe executed such that the condition of the above-described percentages(the first adjustment percentage and the second adjustment percentage)in consideration of a time period from the time at which theoperation-starting time TU has been set to the operation-starting timeTU.

The controller 30 is able to execute the temperature adjustment processon the basis of the process shown in FIG. 13.

In step S401 shown in FIG. 13, the controller 30 initiates thetemperature adjustment process at the time of initiating externalcharging. When it is possible to supply electric power, supplied fromthe commercial power supply 28, to the temperature adjustment device 41,it is possible to initiate the temperature adjustment process beforeexternal charging is initiated.

In step S402, the controller 30 executes the temperature adjustmentprocess until the charging completion time Te. As described in thepresent embodiment, it is possible to execute the temperature adjustmentprocess while carrying out external charging. On the other hand, it ispossible to carry out external charging and execute the temperatureadjustment process alternately. The temperature adjustment process isnot executed when external charging is being carried out, and externalcharging is not carried out when the temperature adjustment process isbeing executed.

In step S403, the controller 30 determines whether the midnight ratetermination time TMe is later than the charging completion time Te. Whenthe midnight rate termination time TMe is earlier than or equal to thecharging completion time Te, the controller 30 completes the processshown in FIG. 13. In this case, it is possible to execute thetemperature adjustment process until the charging completion time Te.

When the midnight rate termination time TMe is later than the chargingcompletion time Te, the controller 30 determines in step S404 whetherthe midnight rate termination time TMe is earlier than theoperation-starting time TU. When the midnight rate termination time TMeis earlier than the operation-starting time TU, the controller 30executes the temperature adjustment process until the midnight ratetermination time TMe in step S405. That is, the temperature adjustmentprocess is executed until the midnight rate termination time TMe evenafter passage of the charging completion time Te. When the midnight ratetermination time TMe is later than or equal to the operation-startingtime TU, the controller 30 executes the temperature adjustment processuntil the operation-starting time TU in step S406. That is, thetemperature adjustment process is executed until the operation-startingtime TU even after passage of the charging completion time Te.

When the temperature adjustment process is executed until theoperation-starting time TU, the target temperature Ktarg is set. Thus,it is possible to bring the battery temperature Kb at theoperation-starting time TU to the target temperature Ktarg by executingthe temperature adjustment process. When the battery temperature Kb hasreached the target temperature Ktarg earlier than the operation-startingtime TU through the temperature adjustment process and then the batterytemperature Kb is kept at the target temperature Ktarg, it is notrequired to execute the temperature adjustment process. Therefore, thetemperature adjustment process may complete earlier than theoperation-starting time TU, and the temperature adjustment process maynot be executed thereafter. On the other hand, when the temperatureadjustment process is not executed until the operation-starting time TU,the corrected temperature Kcorr is set. Thus, even when it is notpossible to execute the temperature adjustment process until theoperation-starting time TU, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Ktarg.

With the process shown in FIG. 13, it is possible to execute thetemperature adjustment process while external charging is being carriedout. With the process shown in FIG. 11, when external charging iscarried out by utilizing the midnight time period, it is possible toactively utilize electric power from the commercial power supply 28 inthe midnight time period. Therefore, even when the temperatureadjustment process is executed together with external charging, it ispossible to actively utilize electric power from the commercial powersupply 28 in the midnight time period, so it is possible to reduce acost of electricity required to execute the temperature adjustmentprocess.

In the present embodiment, the cost of electricity is varied between themidnight time period and the time period other than the midnight timeperiod; however, the cost of electricity is not limited to thisconfiguration. Specifically, the invention is applicable to the casewhere mutually different costs of electricity are set for three or moretime periods. In this case, it is possible to carry out externalcharging or execute the temperature adjustment process as describedabove by separating into a time period during which a cost ofelectricity is the lowest (referred to as lowest rate time period) and atime period other than the lowest rate time period. The lowest rate timeperiod corresponds to the midnight time period described in the presentembodiment, and the time period other than the lowest rate time periodcorresponds to the time period other than the midnight time period,described in the present embodiment.

The invention is also applicable to the case where there are a pluralityof lowest rate time periods in a day. The fact that there are aplurality of lowest rate time periods means that there is a time periodother than the lowest rate time period, between the two lowest rate timeperiods. In this case as well, it is possible to carry out externalcharging on the basis of the process shown in FIG. 11.

Specifically, in the process of step S302 shown in FIG. 11, it is justrequired to be determined whether there is at least one lowest rate timeperiod between the current time Tc and the charging completion time Te.In the process of step S304, it is just required to be determinedwhether it is possible to initiate and complete external charging withinthe at least one lowest rate time period present between the currenttime Tc and the charging completion time Te. With the process shown inFIG. 11, it is possible to carry out external charging by activelyutilizing the at least one lowest rate time period. Thus, it is possibleto reduce a cost of electricity required to carry out external charging.

On the other hand, when there is a plurality of lowest rate time periodsin a day, it is possible to execute the temperature adjustment processon the basis of the process shown in FIG. 13. The midnight ratetermination time TMe that is used in the processes of step S403 and stepS404 shown in FIG. 13 becomes the termination time of the temporallyclosest lowest rate time period with respect to the charging completiontime Te or the operation-starting time TU. As described above, whenexternal charging is carried out by actively utilizing the at least onelowest rate time period, it is possible to actively utilize the at leastone lowest rate time period even when the temperature adjustment processis executed. Thus, it is possible to reduce a cost of electricityrequired to execute the temperature adjustment process. As described inthe process shown in FIG. 13, it is possible to bring the batterytemperature Kb at the operation-starting time TU to, the targettemperature Ktarg.

In the example shown in FIG. 14A and FIG. 14B, there are two lowest ratetime periods by the operation-starting time TU. As shown in FIG. 14A, ifexternal charging is continued and is completed at the chargingcompletion time Te, not only the lowest rate time period but also thetime period other than the lowest time period is included within theperiod during which external charging is carried out. On the other hand,according to the present embodiment, as shown in FIG. 14B, it ispossible to complete external charging at the charging completion timeTe by actively utilizing the lowest rate time periods. Therefore, whenexternal charging is carried out as shown in FIG. 14B, it is possible toreduce a cost of electricity required to carry out external charging ascompared to when external charging is carried out as shown in FIG. 14A.

As shown in FIG. 14A, in order to bring the battery temperature Kb atthe operation-starting time TU to the target temperature Ktarg, when thecooling process is executed until the operation-starting time TU, thecooling process is executed in the time period other than the lowestrate time period. On the other hand, according to the presentembodiment, as shown in FIG. 14B, it is possible to bring the batterytemperature Kb at the operation-starting time TU to the targettemperature Kb by executing the cooling process by actively utilizingthe lowest rate time periods. Therefore, when the cooling process isexecuted as shown in FIG. 14B, it is possible to reduce a cost ofelectricity required to execute the cooling process as compared to whenthe cooling process is executed as shown in FIG. 14A. FIG. 14A and FIG.14B show the cases where the cooling process is executed. Even when theheating process is executed, it is possible to reduce a cost ofelectricity required to carry out external charging or execute theheating process according to the present embodiment.

What is claimed is:
 1. An electrical storage system comprising: anelectrical storage device mounted on a vehicle and configured to becharged with electric power supplied from a commercial power supply, thecommercial power supply being set such that a cost of electricity of afirst time period is lower than a cost of electricity of a second timeperiod; a temperature adjustment device configured to adjust atemperature of the electrical storage device upon reception of electricpower supplied from the commercial power supply; and a controllerconfigured to control charging of the electrical storage device andoperation of the temperature adjustment device, the controller beingconfigured to complete charging of the electrical storage device byoperation-starting time, which is scheduled time at which a start-up ofthe vehicle is initiated, while increasing a percentage of a chargingtime of the electrical storage device in the first time period ascompared to a percentage of the charging time in the second time periodwhen the first time period and the second time period are includedwithin a period from when a user sets the operation-starting time to theoperation-starting time, and the controller being configured to operatethe temperature adjustment device such that a temperature of theelectrical storage device at the operation-starting time falls within atarget temperature range while increasing a percentage of an operatingtime of the temperature adjustment device in the first time period ascompared to a percentage of the operating time in the second time periodwhen the first time period and the second time period are includedwithin the period from when the operation-starting time is set to theoperation-starting time.
 2. The electrical storage system according toclaim 1, wherein the controller is configured to estimate a temperaturevariation in the electrical storage device in a period from when theoperation of the temperature adjustment device is completed to theoperation-starting time on the basis of a temperature of a surroundingenvironment of the electrical storage device when the controllercompletes the operation of the temperature adjustment device earlierthan the operation-starting time, and the controller is configured toincrease the temperature of the electrical storage device at the time ofcompleting the operation of the temperature adjustment device ascompared to an upper limit value of the target temperature range by thetemperature variation by heating the electrical storage device with thetemperature adjustment device when the temperature variation is avariation of a decrease in the temperature of the electrical storagedevice.
 3. The electrical storage system according to claim 2, whereinthe controller is configured to increase the temperature of theelectrical storage device at the time of completing the operation of thetemperature adjustment device within a limit of an upper limittemperature that is allowed by the electrical storage device.
 4. Theelectrical storage system according to claim 1, wherein the controlleris configured to estimate a temperature variation in the electricalstorage device in a period from when the operation of the temperatureadjustment device is completed to the operation-starting time on thebasis of a temperature of a surrounding environment of the electricalstorage device when the controller completes the operation of thetemperature adjustment device earlier than the operation-starting time,and the controller is configured to reduce the temperature of theelectrical storage device at the time of completing the operation of thetemperature adjustment device as compared to a lower limit value of thetarget temperature range by the temperature variation by cooling theelectrical storage device with the temperature adjustment device whenthe temperature variation is a variation of an increase in thetemperature of the electrical storage device.
 5. The electrical storagesystem according to claim 1, wherein the controller is configured tooperate the temperature adjustment device while charging the electricalstorage device with electric power from the commercial power supply. 6.The electrical storage system according to claim 1, wherein thecontroller is configured to operate the temperature adjustment deviceuntil the first time period termination time, when conditions i) and ii)are both satisfied: i) a condition that the first time periodtermination time is later than a charging completion time; and ii) acondition that the first time period termination time is earlier thanthe operation-starting time.
 7. The electrical storage system accordingto claim 1, wherein the controller is configured to operate thetemperature adjustment device until the operation-starting time, whenconditions i) and ii) are both satisfied: i) a condition that the firsttime period termination time is later than a charging completion time;and ii) a condition that the first time period termination time is laterthan the operation-starting time.